The invention relates to a clamping device for expanding a threaded bolt by pulling on the threaded end portion thereof, comprising a support pipe which is supported as an abutment against an underlay which surrounds the threaded bolt, a cylindrical housing which is arranged in extension of the support pipe and which has at least one piston which can be moved therein in the longitudinal direction and which can be connected to a hydraulic supply line, a changeable bushing which is constructed so as to be able to be axially carried by the piston and which, for screwing to the threaded end portion of the threaded bolt, is provided with an inner thread and, for axial carrying by means of the piston, is provided with a radially expanded portion, a resilient arrangement which is arranged around the changeable bushing and which acts axially on the piston, and a lid which is secured to the cylindrical housing and on the lower side of which the other support of the resilient arrangement is constructed.
A generic clamping device for threaded bolts is known from US 2010/0175240 A1. In order to expand the threaded bolt, there is arranged in the cylindrical housing of the clamping device a changeable bushing which is provided at the lower end thereof with an inner thread for screwing to the threaded bolt. The changeable bushing can be carried axially by means of a piston of the clamping device, which piston is acted on hydraulically, and is provided for this purpose with a radially expanded flange or collar. A resilient arrangement which is arranged around the changeable bushing is supported from above against the changeable bushing or against the piston. A replacement of the changeable bushing is possible but requires inter alia that the resilient arrangement be removed.
Also with a clamping device known from US 2011/0271798 A1, the expansion of the threaded bolt is carried out by means of a changeable bushing which engages in the thread of the threaded bolt. It can be axially carried by means of the piston of the clamping device by the changeable bushing being provided close to the upper end thereof with an outer thread, onto which a carrier ring under which the piston engages can be screwed. A resilient arrangement which is arranged around the changeable bushing is supported on the carrier ring and additionally on the changeable bushing which is provided for this purpose with a step which is inwardly recessed. In order to screw the changeable bushing to the threaded bolt, the clamping device is placed on the screw connection and rotated about the axis thereof whereby the changeable bushing is screwed onto the free threaded portion of the threaded bolt. Such a screwing action with the clamping device being rotated about the axis thereof is time-consuming and in view of the weight of such screw clamping devices is also difficult.
For the clamping devices according to US 2010/0175240 A1 and US 2011/0271798 A1, it is always the case that a replacement of the changeable bushing, for instance for a changeable bushing with a different thread geometry or a different length, is connected with a relatively high level of complexity.
An object of the invention is therefore to provide a clamping device, in which the screwing and unscrewing of the changeable bushing can be carried out in a simple and rapid manner, even with regard to a replacement of the changeable bushing.